Hi Steve
You should not need to remove the wheel arches to change plugs. I`ve just done mine no real problem , just thankful my hands weren`t any bigger. The plug spanner used is the key to making life easy, the one I used was a short type which I could get a swan-neck ring spanner on also able to use a small ratchet on some. I always tackle this job on a newly acquired motor with a certain amount of trepidation as you never know what problems you might find (ie damaged threads, seized plugs). What I did find was that the person who was handsomely paid to rebuild the engine for the PO chose to install a mix of plug types being 5x BPR 6 ES and 3x BP 6 ES. These were replaced with a new set of NGK BPR 6 ES set at 35 thou after I`d cleaned the area around the plug-hole making sure non dropped into the engine. As you stated you need to assess the leads, I found one that was totaly out of round where it clipped onto the cap,or should I say it didn`t. Sorry I can`t agree with your theory of setting the gap small and leaving it widen in time, as you state in your last post the plugs can tell you so much about the engines condition plus plugs left for a long time are not easily removed .
Upon firing up the difference was noticeable immediately , quicker starting , engine sounded more powerful and I was able to let it tick over without blipping the throttle far sooner than previous. Just like to add here that although there is a choke fitted to the dash it never actually made it
to the carb must have happened when it had new chassiss fitted, will sort sometime.
Trevor